Compressors

71. Maximum delivery pressure is a rotary air compressor is of the order of

  1. 6 kg/cm2
  2. 10 kg/cm2
  3. 16 kg/cm2
  4. 25 kg/cm2
  5. 40 kg/cm2.

Correct answer: (B)
10 kg/cm2

72. Maximum temprature in a gas turbine is of the order of COMPRESSORS, GAS TURBINES AND JET ENGINES

  1. 2500°C
  2. 2000°C
  3. 1500°C
  4. 1000°C
  5. 700°C.

Correct answer: (E)
700°C.

73. Maximum work is done in compressing air when the compression is

  1. isothermal
  2. adiabatic
  3. polytropic
  4. any one of the above
  5. none of the above.

Correct answer: (B)
adiabatic

74. Mechanical efficiency of gas turbines as compared to I.C engines is

  1. higher
  2. lower
  3. same
  4. depends on on odier considerations
  5. unpredictable.

Correct answer: (A)
higher

75. Mining industry usually employs following motive power

  1. A.C. electric motor
  2. compressed air
  3. petrol engine
  4. diesel engine
  5. D.C. electric motor.

Correct answer: (B)
compressed air

76. More than one stage will be preferred for reciprocating compressor if the delivery pressure is more than

  1. 2 kg/cm2
  2. 6 kg/cm2
  3. 10 kg/cm2
  4. 14.7 kg/cm2
  5. none of the above.

Correct answer: (A)
2 kg/cm2

77. Open cycle gas turbine works on

  1. Brayton or Atkinson cycle
  2. Rankine cycle
  3. Carnot cycle
  4. Erricsson cycle
  5. Joule cycle.

Correct answer: (A)
Brayton or Atkinson cycle

78. Out of the following, from where you will prefer to take intake for air compressor

  1. from an air conditioned room maintained at 20°C
  2. from outside atmosphere at 1°C
  3. from coal yard side
  4. from a side where cooling tower is located nearby
  5. from any one of the above locations.

Correct answer: (D)
from a side where cooling tower is located nearby

79. Phenomenon of choking in compressor means

  1. no flow of air
  2. fixed mass flow rate regardless of pressure ratio
  3. reducing mass flow rate with increase in pressure ratio
  4. increased inclination of chord with air steam
  5. does not occur.

Correct answer: (B)
fixed mass flow rate regardless of pressure ratio

80. Pick up the correct statement

  1. gas turbine uses low air-fuel ratio to economise on fuel
  2. gas turhine uses high air-fuel ratio to reduce outgoing temperature
  3. gas turbine uses low air-fuel ratio to develop the high thrust required
  4. all of the above
  5. none of the above.

Correct answer: (B)
gas turhine uses high air-fuel ratio to reduce outgoing temperature

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